There are numerous prior art external systems disclosures using video and or laser systems to analyze the golf swing. There are also numerous golf club attached systems using shaft mounted strain gauges and or single to multiple accelerometers and gyros to calculate golf swing metrics. However, none of these prior art approaches contemplate a mobile system with only accelerometers attached to the club head orthogonally configured on a three-dimensional axes and use receiver signal strength measurements to correlate time line measurements with the spatial domain.
U.S. Pat. No. 3,945,646 to Hammond integrates three-dimensional orthogonal axes accelerometers in the club head, and describes a means for wirelessly transmitting and receiving the resulting sensor signals. However, he does not contemplate the computational algorithms involving the multi-lever mechanics of a golf club swing required to solve for all the angles of motion of the club head during the swing with a varying swing radius. His premise of being able to obtain face angle only with data from his sensors 13, and 12 (x and y directions respectively described below) is erroneous, as for one example, the toe down angle feeds a large component of the radial centrifugal acceleration onto sensor 12 which he does not account for. He simply does not contemplate the effects of the dynamically changing orientation relationship between the inertial acceleration forces and the associated coordinate system acting on the club head constrained by the multi-lever golf swing mechanics and the fixed measurement coordinate system of the three orthogonal club head sensors.
U.S. Pat. No. 7,672,781 to Churchill uses receiver signal strength measurements with multiple directional antennas in combination with linear calculation methods based on acceleration measurements to determine the location of a movable bodies that could be a golf club. Churchill fails to contemplate using RSSI measurements without the use of directional sectorized antennas in combination with acceleration measurements analysis applied to a movable object with non-linear travel.
The prior art disclosures all fail to offer a golf free swing analysis system that measures only acceleration forces on three orthogonal axes at the club head and interprets that limited data within the constraints of a multi-lever golf swing model using rigid and non rigid levers describing the mechanics of a swing, to determine the dynamically changing orientation relationship of inertial forces experienced at the club head and the orthogonal measurement axes fixed to the club head, resulting in the ability to accurately calculate numerous golf swing metrics over a time line and in addition correlate that time line with the spatial domain